/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the  "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id$
 */
package wx.xml.xalan.xpath.functions;

import wx.xml.xalan.xml.dtm.DTM;
import wx.xml.xalan.xpath.XPathContext;
import wx.xml.xalan.xpath.objects.XBoolean;
import wx.xml.xalan.xpath.objects.XObject;

/**
 * Execute the Lang() function.
 *
 * @xsl.usage advanced
 */
public class FuncLang extends FunctionOneArg {
    static final long serialVersionUID = -7868705139354872185L;

    /**
     * Execute the function.  The function must return
     * a valid object.
     *
     * @param xctxt The current execution context.
     * @return A valid XObject.
     * @throws javax.xml.transform.TransformerException
     */
    public XObject execute(XPathContext xctxt) throws javax.xml.transform.TransformerException {

        String  lang   = m_arg0.execute(xctxt).str();
        int     parent = xctxt.getCurrentNode();
        boolean isLang = false;
        DTM     dtm    = xctxt.getDTM(parent);

        while (DTM.NULL != parent) {
            if (DTM.ELEMENT_NODE == dtm.getNodeType(parent)) {
                int langAttr = dtm.getAttributeNode(parent, "http://www.w3.org/XML/1998/namespace", "lang");

                if (DTM.NULL != langAttr) {
                    String langVal = dtm.getNodeValue(langAttr);
                    // %OPT%
                    if (langVal.toLowerCase().startsWith(lang.toLowerCase())) {
                        int valLen = lang.length();

                        if ((langVal.length() == valLen)
                            || (langVal.charAt(valLen) == '-')) {
                            isLang = true;
                        }
                    }

                    break;
                }
            }

            parent = dtm.getParent(parent);
        }

        return isLang ? XBoolean.S_TRUE : XBoolean.S_FALSE;
    }
}
